Wires, more particularly guidewires, are used in medical procedures to guide medical instruments and treatment devices, such as catheters, stents, embolic protection devices (EPD), etc., into and through small body lumens. For example, an EPD filter is typically inserted over or together with a guidewire using a delivery catheter. Following the treatment procedure, the filter is collapsed and removed from the body over the guidewire or together with the guidewire. Additional treatment devices, such as balloons and stents, can be inserted and removed via the same guidewire.
The distal end of the guidewire is in most situations unsupported in the lumen, so that insertion of the medical instruments and treatment devices may cause unwanted movement of the guidewire and even dislodgement of the guidewire. This problem may be exacerbated when heavier devices are advanced over the guidewire.
Other types of wires used in medical procedures are electrical leads for electrical stimulation therapy to treat a variety of symptoms or conditions such as cardiac arrhythmias, chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, or gastroparesis. One or more stimulation leads are typically percutaneously or surgically implanted in a patient on a temporary or permanent basis, with at least one stimulation electrode being positioned proximate to a target stimulation site. The target stimulation site may be, for example, a spinal cord, pelvic nerve, pudendal nerve, stomach, muscle, or within a brain, the heart or another organ of a patient. For example, the electrodes may deliver stimuli for cardiac resynchronization therapy (CRT).
In most cases, the electric leads are attached to the target organ, such as a cardiac vein or artery, by an anchoring a component located at the tip of the lead in form of, for example, a threaded fixation structure or extendable fixation devices located near the tip, an inflatable balloon, etc. While fixation of pacemaker leads in the right ventricle is successful in most cases, stable fixation within certain vasculature in the human body, such as the coronary sinus for CRT applications, have proven more difficult. Improper lead implantation can sometimes occur during deployment, due to tortuous venous anatomy. Occasionally, lead implantation results in complications, such as coronary sinus dissection or phrenic nerve stimulation.
Lead migration sometimes occurs subsequent to implantation, due to inadequate anchoring mechanisms. With the introduction of biventricular pacing, leads also had to be permanently placed in the cardiac veins, so that fixating electrodes within the vein has become an important clinical problem. The thin wall of the vein does not support the use of screws for fixation, and the smooth vascular wall does not readily support the use of mechanical friction fixating devices. Currently, several methods have been reported to fixate electrical leads in a cardiac vein; however, lead migration still remains a significant clinical problem.
With current technologies, the fixation structure or fixation devices are permanently attached to or incorporated in the electrical lead and in most cases form the tip of the lead. This arrangement makes it impossible to later move the tip of the lead relative to the fixation structure, for example, to improve coupling between the lead tip and the treatment site.
Accordingly, there is a need for improved lead fixation in a body lumen, wherein positioning of the electrical lead or the guidewire is independent of placement of the fixation structure, and wherein possibilities exist for later repositioning the tip of the wire or guidewire relative to the fixation structure, without moving the fixation structure inside the body lumen.